Analytic expressions for maximum chemical concentration attained in plants, and time this takes for uptake from surrounding soil were derived from a simple two-compartment soil/water-plant model. To illustrate, for the antibiotic norflxacin undergoing first order loss in the soil/water phase with a rate constant of 0.544 days-1, maximum concentration in soybean PMAX is predicted to occur after 2.79 days exposure and be independent of initial soil/water concentration SW0 of 52.5 mg kg-1 dry weight. For soybean, the relationship between PMAX and SW0 is PMAX = 0.047SW0, resulting in predicted maximum levels of 2.20 mg kg-1 dry weight. Modelled plant concentrations agreed well with experimental data (R2 = 0.91).